Polycarbonate and resin composition

ABSTRACT

The present invention relates to a polycarbonate which can be obtained by a melting method and has a viscosity-average molecular weight of 16000 to 27000, and whose loss angle δ and complex viscosity η* (Pa·s) measured under the conditions of 250° C. and an angular velocity of 10 rad/s satisfy the following relation (1): 
     
       
         4,700≦Tan δ/(η*) −0.87   (1)

BACKGROUND OF THE INVENTION

The present invention relates to a polycarbonate, more particularly to apolycarbonate having excellent impact resistance at low temperature anda resin composition containing the said polycarbonate.

Polycarbonates are widely used in many fields of industries as a resinwith many advantageous properties such as high heat resistance, impactresistance and transparency. As to a method for producingpolycarbonates, an interfacial method comprising reacting directly anaromatic dihydroxy compound such as bisphenol A with phosgene isgenerally used. However, in the interfacial method, there arise theproblems such as poor thermal stability of the said polycarbonate andthe corrosion of the mold at the time of injection molding caused byremaining methylene chloride in the polycarbonate. Therefore, a meltingmethod comprising reacting an aromatic dihydroxy compound with acarbonic acid diester has been evaluated again because in addition tothe advantages that there are no problems mentioned above in theinterfacial method, polycarbonates can be produced by the melting methodmore inexpensive than those by the interfacial method.

However, comparing with the polycarbonate produced by the interfacialmethod, the polycarbonate produced by the melting method tends to reduceimpact strength at low temperature, so that the polycarbonate is limitedin practical use in which the impact strength at low temperature isespecially required, such as automobile parts and OA equipment parts. Asa method for improving the impact strength at low temperature ofpolycarbonate produced by the melting method, there are generally used amethod of increasing the molecular weight and a method in which variouselastomers are added into the polycarbonate. However, the molded articleobtained by these methods has problems that flowabilty of polycarbonateis poor, color tone thereof is deteriorated and transparency thereof isdeteriorated as the case.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a polycarbonate havingexcellent impact resistance at low temperature and a resin compositioncontaining the said polycarbonate.

As a result of the present inventor is earnest studies to attain theabove object, it has been found that a polycarbonate obtained by amelting method and having a specific molecular weight and a specificmelt viscoelasticity has better impact strength at low temperature thanthe other types of polycarbonate having the substantially same molecularweight. The present invention has been attained on the basis of theabove finding.

Thus, in the first aspect of the present invention, there is provided apolycarbonate which can be obtained by a melting method and has aviscosity-average molecular weight of 16000 to 27000, and whose lossangle δ and complex viscosity η* (Pa·s) measured under the conditions of250° C. and an angular velocity of 10 rad/s satisfy the followingrelation (1):

4,700≦Tan δ/(η*)^(−0.87)  (1)

In the second aspect of the present invention, there is provided apolycarbonate resin composition comprising a polycarbonate (as definedin the first aspect) which can be obtained by a melting method and has aviscosity-average molecular weight of 16000 to 27000, and whose lossangle δ and complex viscosity η* (Pa·s) measured under the conditions of250° C. and an angular velocity of 10 rad/s satisfy the followingrelation (1):

4,700≦Tan δ/(η*)^(−0.87)  (1)

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a flow sheet showing an example of the production methodaccording to the present invention.

Each reference number used in the drawing shows as follows.

1: DPC tank, 2: agitator, 3: BPA hopper, 4 a, 4 b: material mixingtanks, 5: DPC flow rate control valve, 6: BPA flow rate control valve,7: pump, 8: catalyst flow rate control valve, 9: program control unit,10: pump, 11: catalyst tank, 12: by-product discharge pipe, 13 a, 13 b,13 c: vertical polymerizers, 14: Max Blend agitator, 16: gate paddleagitator.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described in detail below.

The polycarbonate according to the present invention is produced by amelting method using an aromatic dihydroxyl compound and a carbonic aciddiester as starting materials.

Aromatic Hydroxyl Compounds

The aromatic hydroxyl compounds that can be used as one of the startingmaterials in the process of the present invention are the compoundsrepresented by the following chemical formula (1)

wherein A is an optionally substituted single-bond C₁-C₁₀ linear,branched or cyclic divalent hydrocarbon group, or a divalent grouprepresented by —O—, —S—, —CO— or —SO₂—; X and Y are each a halogen atomor a C₁-C₆ hydrocarbon group; p and q are each an integer of 0 or 1, inwhich X and Y, and p and q, may be identical or different.

Representative examples of the said aromatic dihydroxyl compounds arebis(4-hydroxydiphenyl)methane, 2,2-bis(4-hydroxyphenyl)propane,2,2-bis(4-hydroxy-3-methylphenyl)propane,2,2-bis(4-hydroxy-3-t-butylphenyl)propane,2,2-is(4-hydroxy-3,5-dimethylphenyl)propane,2,2-bis(4-hydroxy-3,5-dibromophenyl)propane,4,4-bis(4-hydroxyphenyl)heptane, 1,1-bis(4-hydroxyphenyl) cyclohexane,4,4′-dihydroxybiphenyl, 3,3′,5,5′-tetramethyl-4,4′-dihydroxybiphenyl,bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl) sulfide,bis(4-hydlroxyphenyl) ether, and bis(4-hydroxyphenyl) ketone. Thesearomatic dihydroxyl compounds may be used either singly or as acombination of two or more. Of these compounds,2,2-bis(4-hydroxyphenyl)propane (which may hereinafter be called“bisphenol A” and may be abbreviated as “BPA”) is preferred.

Carbonic Acid Diesters

The carbonic acid diesters usable as another starting material in thepresent invention are the compounds represented by the followingchemical formula (2).

wherein A′ is an optionally substituted C₁-C₁₀ linear, branched orcyclic monovalent hydrocarbon group, and two A′s may be identical ordifferent.

Typical examples of the said carbonic acid diesters are diphenylcarbonate, substituted diphenyl carbonates such as ditolyl carbonate,and dialkyl carbonates such as dimethyl carbonate, diethyl carbonate anddi-t-butyl carbonate. These carbonic acid diesters may be used eithersingly or by mixing two or more of them. Of these compounds, diphenylcarbonate (which may hereinafter be abbreviated as “DPC”) andsubstituted diphenyl carbonate are preferred.

The said carbonic acid diesters may be substituted, by an amount ofpreferably not more than 50% by mole, more preferably not more than 30%by mole, with a dicarboxylic acid or a dicarboxylic acid ester. Typicalexamples of such dicarboxylic acids or dicarboxylic acid esters areterephthalic acid, isophthalic acid, diphenyl terephthalate, anddiphenyl isophthalate. When the carbonic acid diesters are substitutedwith such dicarboxylic acids or dicarboxylic acid esters, there areobtained polyester carbonates.

These carbonic acid diesters (which include the substituted dicarboxylicacids and dicarboxylic acid esters) are usually used in an excess amountover the aromatic dihydroxyl compound, specifically in a molar ratio tothe aromatic dihydroxyl compound in the range of 1.001 to 1.3,preferably 1.01 to 1.2. When the molar ratio of the carbonic aciddiester to the aromatic dihydroxyl compound is less than 1.001, theterminal OH groups of the produced polycarbonate are increased todeteriorate its thermal stability and hydrolytic resistance. When thesaid molar ratio exceeds 1.3, although the terminal OH groups of theproduced polycarbonate are decreased, there arises a tendency for theester exchange reaction to slow down under the same conditions, makingit hard to produce a polycarbonate having the desired molecular weight.In the present invention, a polycarbonate with its terminal OH groupcontent falling within the range of 50 to 1,000 ppm is preferably used.

Concerning the way of supply of the starting materials to their mixingtank, in view of the fact that higher metering precision is providedwhen the materials are in a liquid state, preferably one or both of thestarting materials (an aromatic dihydroxyl compound and a carbonic aciddiester) are melted and supplied in a liquid state. In case where thestarting material(s) is(are) supplied in a liquid state, an ovalflowmeter, micro-motion flowmeter or the like can be used as feed meter.

In case of supplying the materials in a solid state, it is morepreferable to use a meter of the weight measuring type, such as belttype or loss-in-weight type weight feeder, than to use a volumemeasuring type such as screw feeder. Of these, the loss-in-weight typeis especially preferred.

Ester Exchange Catalysts

Usually a catalyst is used in producing polycarbonates by the meltingmethod. In the polycarbonate production process of the presentinvention, although the type of the catalyst used is not specified,generally alkali metal compounds, alkaline earth metal compounds andbasic compounds such as basic boron compounds, basic phosphoruscompounds, basic ammonium compounds and amine-based compounds are used.These compounds may be used singly or as a combination of two or more.

Catalyst is used in an amount within the range of 0.05 to 4 μmol,preferably 0.08 to 3 μmol, more preferably 0.1 to 2 μmol, based on moleof the aromatic dihydroxyl compound. If the amount of the catalyst usedis below the above-defined range, there may not be obtained sufficientpolymerization activity for producing a polycarbonate of the desiredmolecular weight, while if the catalyst amount exceeds the above-definedrange, the produced polymer may be poor in hue, and also branching ofthe polymer may advance to cause a reduction of fluidity required at thetime of molding.

Examples of the alkali metal compounds usable as catalyst in the presentinvention include inorganic alkali metal compounds such as hydroxides,carbonates and hydrogencarbonates of lithium, sodium, potassium,rubidium and cesium, and organic alkali metal compounds such asalcoholates, phenolates and organic carboxylates. Of these alkali metalcompounds, cesium compounds, especially cesium carbonate, cesiumhydrogencarbonate and cesium hydroxide are preferred.

Examples of the alkaline earth metal compounds include inorganicalkaline earth metal compounds such as hydroxides and carbonates ofberyllium, magnesium, calcium, strontium and barium, and organicalkaline earth metal compounds such as alcoholates, phenolates andorganic carboxylates.

Examples of the basic boron compounds include sodium salts, potassiumsalts, lithium salts, calcium salts, magnesium salts, barium salts andstrontium salts of tetramethylboron, tetraethylborone, tetrapropylboron,tetrabutylboron, trimethylethylboron, trimethylbenzylboron,trimethylphenylboron, triethylmethylboron, triethylbenzylboron,triethylphenylboron, tributylbenzylboron, tributylphenylboron,tetraphenylboron, benzyltriphenylboron, methyltriphenylboron andbutyltriphenylboron.

Examples of the basic phosphorus compounds include trivalent phosphoruscompounds such as triethylphosphine, tri-n-propylphosphine,tri-i-propylphosphine, tri-n-butylphosphine, triphenylphosphine andtributylphosphine, and quaternary salts derived from these compounds.

Examples of the basic ammonium compounds include tetramethylammoniumhydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide,tetrabutylammonium hydroxide, trimethylethylammonium hydroxide,trimethylbenzylammonium hydroxide, trimethylphenylammonium hydroxide,triethylmethylammonium hydroxide, triethylbenzylammonium hydroxide,triethylphenylammonium hydroxide, tributylbenzylammonium hydroxide,tributylphenylammonium hydroxide, tetraphenylammonium hydroxide,benzyltriphenylammonium hydroxide, methyltriphenylammonium hydroxide,and butyltriphenylammonium hydroxide.

Examples of the amine-based compounds include 4-aminopyridine,2-aminopyridine, N,N-dimethyl-4-aminopyridine, 4-diethylaminopyridine,2-hydroxypyridine, 2-methoxypyridine, 4-methoxypyridine,2-dimethylaminoimidazole, 2-methoxyimidazole, imidazole,2-mercaptoimidazole, 2-methylimidazole and aminoquinoline.

Of these catalysts, alkali metal compounds are preferred for practicaluse.

In the present invention, ester exchange catalyst is used as a solventsolution. As solvent, there can be used, for example, water, acetone,alcohol, toluene, phenol, and other solvents capable of dissolving thearomatic dihydroxyl compound and carbonic acid diester used as startingmaterials. Of these solvents, water is preferred, and especially when analkali metal compound is used as catalyst, it is preferably used as anaqueous solution.

The polycarbonate according to the present invention essentially has aviscosity-average molecular weight of 16,000 to 27,000, preferably18,000 to 26,000. When the viscosity-average molecular weight is lessthan 16,000, the impact resistance thereof may be reduced. When theviscosity-average molecular weight is more than 27,000, the flowabiltythereof may be deteriorated.

It is an essential requirement for the polycarbonate of the presentinvention that its loss angle δ and complex viscosity η* (its unit isPa·s) measured under the conditions of 250° C. and an angular velocityof 10 rad/s satisfy the following relation (1), preferably the relation(11), more preferably the relation (12). In the present invention, thevalue of Tan δ/(η*)^(−0.87) was used as a parameter indicating meltviscoelasticity of the polycarbonate. When the value of Tanδ/(η*)^(−0.87) is less than 4,700, the impact strength at lowtemperature may be reduced. When the value of Tan δ/(η*)^(−0.87) is toolarge, the transferability tend to deteriorate. Therefore, Tanδ/(η*)^(−0.87) is preferably not more than 7,500, more preferably notmore than 7,000.

4,700≦Tan δ/(η*)^(−0.87)  (1)

5,000≦Tan δ/(η*)^(−0.87)≦7,500  (11)

5,500≦Tan δ/(η*)^(−0.87)≦7,000  (12)

Loss angle δ indicates the phase lag of strain vis-á-vis stressdetermined from the measurement of dynamic melt viscoelasticity, and itis generally known as one of the indices indicating the dynamicviscoelasticity behavior. A large value of δ(Tan δ) signifies strongviscous nature of viscoelasticity, and a small value of δ signifies tostrong elastic nature. The factors that decide this value are complex,and among such factors are the type of the monomer used, copolymercomposition, copolymer structure, molecular structural propertiesincluding the formula of branching such as number of branch points andlength of branched chain, molecular weight, and molecular weightdistribution.

It has been found with these polycarbonates produced by the interfacialmethod that when the value of δ (Tan δ) is plotted against complexviscosity (η* (Pa·s)), which is an index of molecular weight, etc., inlogarithmic coordinates, the measured values of δ are almost aligned onthe straight line of Tan δ/(η*)^(−0.87)=ca. 8,000. (Here, the number−0.87 which is an index of η* indicates inclination of the said straightline, and Tan δ/(η*)^(−0.87) indicates the value of Tan δ when the abovestraight line was extrapolated to η*=1 (Pa·s). Thus, by using the valueof Tan δ/(η*)^(−0.87) as a parameter, it becomes possible to eliminatemolecular weight (viscosity) dependency of loss angle. Such alignment ofthe δ values is not seen with the polycarbonates produced by the meltingmethod, and it has been further found that the melting methodpolycarbonates with 4,700≦Tan δ/(η*)^(−0.87) are excellent in impactresistance at low temperature.

As the reason why the melt viscoelasticity parameter specified in thepresent invention gives a good effect on impact resistance at lowtemperature of the polycarbonates, the fact may be pointed out that whenthe value of δ (Tan δ) is too small, it is presumed that any undesirableside reaction may occur.

In the present invention, various additives such as stabilizer,ultraviolet absorber, release agent, frame retardant, colorant, etc.,may be contained in the polycarbonate, and these additives may be addedduring production of the polycarbonate or before production of pellets.The products containing these additives may be here generally called“polycarbonates”, but the above-shown relations specified in the presentinvention apply to the polycarbonates which contain none of theseadditives.

Production Method of Polycarbonate

In the present invention, any polycarbonate producing method can be usedas far as it is a melting method and capable of producing apolycarbonate having the above-specified properties. For example, thefollowing method can be used.

Usually, both raw materials are mixed by uniformly stirring in a mixingtank and then polymerized by adding a catalyst to form a polymer.Preferably, both raw materials, viz. an aromatic dihydroxyl compound anda carbonic acid diester, are continuously supplied to a mixing tank, andthe resulting mixture and an ester exchange catalyst are continuouslysupplied together to a polymerizer. For stabilized production of thepolymer having the specified properties of the present invention, amethod which satisfies at least the following two conditions (1) and (2)is used.

(1) The “setting amount of catalyst”, or the target amount of supply ofcatalyst for maintaining the amount of catalyst constant to 1 mole ofthe aromatic dihydroxyl compound or carbonic acid diester supplied tothe polymerizer, is selected from the range of 0.05 to 4 μmol per 1 moleof the aromatic hydroxyl compound for every unit production timeregulated by properly fractionalizing the whole production time. The“whole production time” corresponds to the material supply time forstable production of the polymer in the polymerizer, and does notinclude the polymer production time during the unstable periods such asat the time of start up, switching of grade and end of production.

(2) In at least 95% of each unit production time, the actual amount ofester exchange catalyst supplied (hereinafter referred to simply as“actual amount of catalyst”) is maintained equal to the setting amountof catalyst±0.1 μmol for 1 mole of the aromatic hydroxyl compound.

In the above condition (1), the setting amount of catalyst need not be afixed value throughout the whole production time; the whole productiontime may be fractionalized, and setting may be made for every unitproduction time.

This method is explained in detail below.

In case where the whole production time is a single-fraction unitproduction time, the actual amount of catalyst is maintained at a valueof the setting amount of catalyst±0.1 μmol for 1 mole of the aromaticdihydroxyl compound in at least 95% of the whole production time. Incase where the whole production time is fractionalized into plural unitproduction periods and the setting amount of catalyst is varied, theactual amount of catalyst is maintained at a value of the setting amountof catalyst±0.1 umol in at least 95% of each unit production time. Ineither case, the actual amount of catalyst is preferably maintained at avalue of the setting amount of catalyst±0.08 μmol, more preferably at avalue of the setting amount of catalyst±0.06 μmol. The ratio of theperiod in which the actual amount of catalyst is maintained at acontrolled value should be at least 95% of the whole production time oreach unit production time. The closer to 100% is this ratio, the betterresult can be expected. When the said ratio is less than 95%, it may bedifficult to obtain a polymer having a desired molecular weight and adesired content of terminal OH groups, and particularly when the ratioof the time in which the actual amount of catalyst is more than thesetting amount of catalyst is high, the produced polymer may deterioratein hue and also branching of the polymer advances, so that it may bedifficult to obtain a polymer which satisfies the relations specified inthe present invention. Further, in this case, fluidity at the time ofmolding of the polymer tends to lower. It is possible to produce thepolycarbonate of the present invention even when the productionconditions at the time of polymerization reaction such as polymerizationtemperature, polymerization time and degree of reduction of pressure arechanged, but such change of production conditions is not preferablebecause it may be difficult to produce the polymer stably. It has beenfound that only when the supply of catalyst is continued by maintainingthe actual amount of catalyst within a limited variable range of settingamount of catalyst±0.1 μmol, it becomes possible to stably produce apolymer satisfying the specific relations defined in the presentinvention and having good properties such as narrow molecular weightdistribution and excellent color tone, fluidity, heat resistance,mechanical properties, etc., without requiring any complexpolymerization operation.

In order to maintain the said actual amount of catalyst within the rangeof the setting amount of catalyst±0.1 μmol, it is preferable to supplythe catalyst while metering its flow rate by an appropriate meter suchas oval flowmeter or micro-motion flowmeter.

For automatically controlling the catalyst supply, for example themetered values of the actual catalyst flow rate are successively inputto a computer by which the said setting amount of catalyst is comparedwith the setting flow rate of catalyst calculated from the amount of thearomatic dihydroxyl compound or carbonic acid diester supplied to thematerial preparing tank. If any metered value of the actual flow rate ofcatalyst disagrees with the setting flow rate of catalyst, this resultis transmitted to the catalyst metering/feeding device to adjust thevalve opening so that the actual flow rate of catalyst will agree withthe setting flow rate.

Here, automatic control of catalyst supply based on the successiveintermittent metering system can be conducted in the same way as in thecase of the continuous metering system when due consideration is givento the optimization of metering interval of the actual flow rate ofcatalyst, but continuous automatic metering system is preferred forobtaining the products with stabilized quality. If the catalyst flowrate can be automatically metered continuously, it becomes possible torapidly and continuously control the supply of catalyst to thepolymerizer, and as a result, the setting flow rate of catalyst ismaintained constant, the deflections of viscosity-average molecularweight and terminal OH group content of the polycarbonate are minimized,the molecular weight distribution is narrowed, and there can thus beobtained the products which are uniform in properties such as colortone, fluidity, heat resistance and mechanical properties.

The period in which the actual amount of catalyst remained within therange of the setting amount of catalyst±0.1 μmol in the unit productiontime with a certain setting amount of catalyst can be easily judged fromthe result of metering made by the said metering means. In the case ofcontinuous metering, it is judged whether the actual amount of catalysthas been maintained within the range of the setting amount ofcatalyst±0.1 μmol in at least 95% of the unit production time with thesaid setting amount of catalyst, by determining the cumulative time inwhich the actual amount of catalyst remained in the range of the settingamount of catalyst±0.1 μmol and the cumulative time in which the actualamount of catalyst ran out of the said range, from the curves showingthe relation between the actual amount of the catalyst and the meteringtime. In the case of non-continuous metering, too, the above judgmentcan be made by incorporating statistical calculations or other method ifthe metering is successive.

In the present invention, the polymerization reaction (ester exchangereaction) is generally carried out in two or more polymerizers, that is,in two or more stages, usually 3 to 7 stages continuously, under thefollowing conditions: temperature 150 to 320° C.; pressure normal to1.33 Pa; average residence time =5 to 150 minutes. In each polymerizer,in order to expedite discharge of the phenol formed as a by-product withthe progress of reaction, setting is made so that the temperature andthe degree of vacuum are elevated stepwise while maintaining theabove-defined reaction conditions. It is preferable to set thetemperature as low as possible and the residence time as short aspossible for preventing degradation of qualities such as hue of theproduced polycarbonate.

For automatic control of the actual amount of catalyst in case of usingplural polymerizers for multi-stage reaction, it is preferable that theamount of catalyst supplied be automatically controlled continuously,and in this case, it is necessary that metering and control be completedwithin ⅓ of the residence time of the first polymerizer.

The apparatus used for the said ester exchange reaction may be eithervertical, tubular, tower type or horizontal. Usually, there are providedone or more vertical polymerizers equipped with a turbine impeller,paddle agitator, anchor agitator, Fulzone agitator (produced by ShinkoPantec Co., Ltd.), Sun Meler agitator (produced by Mitsubishi HeavyIndustries Ltd.), Max Blend agitator (produced by Sumitomo HeavyIndustries Ltd.), helical ribbon blender, torsional gate paddle agitator(produced by Hitachi Ltd.) or the like, and successively to thisvertical polymerizer(s), there is provided a horizontal single-shaftpolymerizer such as disc type or cage type, or a horizontal two-shaftpolymerizer equipped with HVR, SCR, N-SCR (produced by Mitsubishi HeavyIndustries Ltd.), Bibolac (produced by Sumitomo Heavy Industries Ltd.),spectacle impeller, gate paddle agitator (produced by Hitachi Ltd.), atwisted or wrenched impeller or a slanted impeller having both functionsof a spectacle impeller and polymer feeder, or a combination thereof.

In the polycarbonate produced in the manner described above, thereusually remain the starting monomeric materials, catalyst, aromatichydroxyl compound and other low-molecular weight compounds such aspolycarbonate oligomers which are formed as by-products in the esterexchange reaction. Particularly the starting monomeric materials andaromatic hydroxyl compound remain in large quantities and give adverseeffect to the properties such as thermal aging resistance and hydrolyticresistance of the product, so that they are preferably removed from theproduct.

The method of removing these residual substances is not specified in thepresent invention; for instance, they may be evaporated away by a ventedextruder. In this case, it is preferable to deactivate the residualbasic ester exchange catalyst in the resin by adding an acidic compoundor its precursor, as this suppresses the side reactions from occurringduring evaporation, allowing efficient removal of the remainingmonomeric materials and aromatic hydroxyl compound in the polymer.

The acidic compound or its precursor to be added in the above operationis not specifically defined; it is possible to use any acidic compoundwhich has the effect of neutralizing the basic ester exchange catalystused for the polycondensation reaction. Examples of such acidiccompounds are Bronsted acids such as hydrochloric acid, nitric acid,boric acid, sulfuric acid, sulfurous acid, hypophosphorus acid,polyphosphoric acid, adipic acid, ascorbic acid, aspartic acid, azelaicacid, adenosinephosphoric acid, benzoic acid, formic acid, valeric acid,citric acid, glycolic acid, glutamic acid, cinnamic acid, succinic acid,acetic acid, tartaric acid, oxalic acid, p-toluenesulfinic acid,p-toluenesulfonic acid, naphthalenesulfonic acid, nicotinic acid, picricacid, picolinic acid, phthalic acid, terephthalic acid, propionic acid,benzenesulfinic acid, benzenesulfonic acid, malonic acid and maleicacid, and their esters. These acids may be used either singly or as acombination of two or more. Of these acidic compounds and theirprecursors, the sulfonic compounds or their esters, for example,p-toluenesulfonic acid, methyl p-toluenesulfonate and butylp-toluenesulfonate are preferred.

Such an acidic compound or its precursor is added in an amount which is0.1 to 50 times, preferably 0.5 to 30 times by mole the neutralizedamount of the basic ester exchange catalyst used for thepolycondensation reaction. The time of addition is free to choose as faras it is posterior to the polycondensation reaction. The way ofaddition, which is also not specifically restricted in the presentinvention, may be properly selected depending on the properties of theacidic compound or its precursor used, required conditions and otherfactors; it is possible to use, for instance, a method in which thecompound or its precursor is added directly, a method in which it isdissolved in a proper solvent and added as such, or a method using apellet or flake-like masterbatch.

The extruder used for the evaporation may be either single-screw type ortwin-screw type. When using a twin-screw extruder, it is preferably anintermeshing screw type, with the screws rotating in the same directionor in the opposite directions. For the purpose of evaporation, theextruder is preferably provided with plural vents in the rear of theacidic compound feed port. The number of the vents is not restricted,but usually 2 to 10 vents are provided. In this extruder, if necessaryadditives such as stabilizer, ultraviolet absorber, release agent,colorant, etc., may be added and kneaded with the resin.

In the present invention, a polycarbonate mixture (C) shown as followsis also preferred. Thus, the polycarbonate mixture (C) mainly comprisesa polycarbonate (A) obtained by a melting method and having aviscosity-average molecular weight of 16000 to 27000, and whose lossangle δ and complex viscosity η* (Pa·s) measured under the conditions of250° C. and an angular velocity of 10 rad/s satisfy the above formula(1); and comprising a polycarbonate (B) obtained by an interfacialmethod, in which the polycarbonate mixture (C) satisfies the aboveformula (1). The polycarbonate mixture (C) also has the same propertiesof polycarbonate (A). Here, “mainly comprise” means comprising in anamount of more than 50% by weight based on the total weight of thepolycarbonate mixture.

Polycarbonate Resin Composition

In the polycarbonate of the present invention, at least one additiveselected from stabilizer, ultraviolet absorber, release agent, flameretardant and colorant may be contained in the polycarbonate as definedin the first aspect, to form a polycarbonate resin composition. Suchadditives are not specifically defined, and those commonly used inpolycarbonates can be used.

The stabilizers usable as additive in the present invention includehindered phenol compounds, phosphorus compounds, sulfur compounds, epoxycompounds and hindered amine compounds. Of these compounds, at least oneantioxidant selected from hindered phenol compounds and phosphoruscompounds is preferably used.

The hindered phenol compound used here is preferably selected from thoserepresented by the following chemical formula (3):

wherein R¹ and R² are each a C₁-C₁₀ hydrocarbon group and may beidentical or different; Y is a C₁-C₂₀ hydrocarbon group which maycontain a functional group selected from ester group, ether group andamide group, and/or a phosphorus atom; Z is a C₁-C₆ hydrocarbon groupwhich may contain an oxygen atom and/or a nitrogen atom, a sulfur atomor a single bond; and g is an integer of 1 to 4.

Examples of such hindered phenol compounds aren-octadecyl-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate,1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate],pentaerythrityl-tetrakis[3(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate],3,9-bis[1,1-dimethyl-2-{β(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane,triethyleneglycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate],3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethylester,1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene,2,2-thio -diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate],tris-(3,5-di-t-butyl-4-hydroxybenzyl)-isocyanurate, and,N′-hexamethylenebis(3,5-di-t-butyl-4-hydroxyhydrocinnamide). Of thesecompounds, n-octadecyl-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate,1,6-hexanediol-bis[3-(3′,5′-t-butyl-4′-hydroxyphenyl)propionate], and3,9-bis[1,1-dimethyl-2-{β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]-2,4,8,10-tetraoxaspiro[5,5]undecaneare preferred.

The phosphorus compound used as stabilizer in the present invention ispreferably a trivalent phosphorus compound, and it is preferably atleast one compound selected from the phosphorous esters which have beenesterified with a phenyl and in which at least one ester has a phenoland/or at least one C₁-C₂₅ alkyl group, and tetrakis(2,4-di-t-butylphenyl)-4,4′-biphenylenediphosphonite. Examples of suchphosphorous esters are 4,4′-butylidene-bis(3-methyl-6-t-butylphenyl-ditridecyl)phosphite, 1,1,3-tris(2-methyl-4-ditridecylphosphite-5-t-butylphenyl)butane, trisnonylphenylphosphite, dinonylphenylpentaerythritol diphosphite,tris(2,4-di-t-butylphenyl) phosphite,bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite,di(2,6-d-t-butyl-4-methylphenyl)pentaerythritol diphosphite,2,2′-ethylidene-bis(4,6-di-t-butylphenyl)fluorophosphite,2,2′-methylene-bis(4,6-di-t-butylphenyl)octylphosphite,bis(2,4-dicumylphenyl)pentaerythritol diphosphite, phosphorous estercomprising monononylphenol and dinonylphenol, and phosphorous estershaving hindered phenols represented by the above-shown formula (3).

In the present invention,tetrakis(2,4-d-t-butylphenyl)-4,4′-biphenylene-diphosphonite,tris(2,4-di-t-butylphenyl) phosphite or2,2′-methylene-bis(4,6-di-t-butylphenyl) octylphosphite are preferablyused as phosphorus compound.

The stabilizer content in the polycarbonate is preferably not more than1 part by weight, more preferably not more than 0.4 part by weight,based on 100 parts by weight of the polycarbonate. If its contentexceeds 1 part by weight, there may arise the problems such asdeterioration of hydrolytic resistance. When two or more types ofstabilizer are used, their mixing ratio may be properly decided. Also,which stabilizer is to be used or whether two or more types ofstabilizer should be used can be properly decided in consideration ofthe purpose of use of the product polycarbonate. Generally, thephosphorus compounds are effective for improving thermal stabilityduring molding of the polycarbonate and for improving thermal stabilityof its molded article, while the phenol compounds are effective forimproving thermal stability such as thermal aging resistance in use ofthe polycarbonate molded articles. Combined use of a phosphorus compoundand a phenol compound contributes to the improvement of tinting.

The ultraviolet absorbers usable in the present invention includeinorganic ultraviolet absorbers such as titanium oxide, cesium oxide andzinc oxide, and organic ultraviolet absorbers such as benzotriazolecompounds, benzophenone compounds and triazine compounds. In the presentinvention, the organic ultraviolet absorbers are preferred, and it isparticularly preferable to use one selected from benzotriazolecompounds, 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]-phenol,2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl]-5-(octyloxy)phenol,2,2′-(1,4-phenylene)bis[4H-3,1-benzoxadine-4-one], and[(4-methoxyphenyl)-methylene]-propanedioic acid-dimethylester.

Preferred examples of the benzotriazole compounds are those representedby the following chemical formula (4), and the condensate ofmethyl-3-[3-t-butyl-5-(2H-benzotriazole-2-yl)-4-hydroxyphenyl]propionateand polyethylene glycol.

wherein R¹ to R⁴ represent independently a hydrogen atom, a halogen atomor a C₁-C₁₂ hydrocarbon group; and Y¹ and y² represent independently ahydrogen atom or a C₁-C₄₀ hydrocarbon group which may contain a nitrogenatom and/or an oxygen atom.

Examples of the benzotriazole compounds of the formula (4) are2-bis(5-methyl-2-hydroxyphenyl)benzotriazole,2-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole,2-(3′,5′-di-t-butyl-2′-hydroxyphenyl)-5-chlorobenzotriazole,2-(3-t-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole,2-(2′-hydroxy-5′-t-octylphenyl)benzotriazole,2-(3,5-di-t-amyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bisα, αdimethylbenzyl)phenyl]-2H-benzotriazole,[methyl-3-[3-t-butyl-5-(2H-benzotriazole-2-yl)-4-hydroxyphenyl]propionate-polyethyleneglycol] condensate, and the compounds represented by the followingchemical formula (5):

Particularly preferred in these compounds are2-(2′-hydroxy-5′-t-octylphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis (α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, the compounds of the formula(5), 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]-phenol, and2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl]-5-(octyloxy)phenol.

The content of ultraviolet absorber in the composition is preferably notmore than 5 parts by weight, more preferably not more than 1 part byweight, based on 100 parts by weight of the polycarbonate. If itscontent exceeds 5 parts by weight, there arise the problems such ascontamination of the mold at the time of injection molding. It ispossible to use either one ultraviolet absorber or two or more ofultraviolet absorbers as a mixture.

As release agent, at least one compound selected from aliphaticcarboxylic acids, aliphatic carboxylic acid esters, aliphatichydrocarbon compounds having a number-average molecular weight of 200 to15,000 and polysiloxane-based silicone oil is used. It is preferred touse at least one compound selected from aliphatic carboxylic acids andaliphatic carboxylic acid esters.

As the aliphatic carboxylic acids usable as release agent in the presentinvention, saturated or unsaturated aliphatic monocarboxylic acids,dicarboxylic acids and tricarboxylic acids can be exemplified. Here, thealiphatic carboxylic acids include alicyclic carboxylic acids. Of thesealiphatic carboxylic acids, mono- or dicarboxylic acids having 6 to 36carbon atoms in the molecule are preferred, and aliphatic saturatedmonocarboxylic acids having 6 to 36 carbon atoms in the molecule aremore preferred. Examples of such aliphatic carboxylic acids are palmiticacid, stearic acid, valeric acid, caproic acid, caprylic acid, lauricacid, arachic acid, behenic acid, lignoceric acid, cerotic acid,melissic acid, montanic acid, glutamic acid, adipic acid, and azelaicacid.

As the aliphatic carboxylic acid moiety of the aliphatic carboxylic acidester, it is possible to use the above-mentioned aliphatic carboxylicacids. As the alcohol moiety of the said ester, saturated or unsaturatedmonohydric alcohols and saturated or unsaturated polyhydric alcohols canbe used. These alcohols may have substituents such as fluorine atom oraryl group. Preferred of these alcohols are mono- or polyhydricsaturated alcohols with a carbon number of not more than 30. Aliphaticsaturated mono- or polyhydric alcohols with a carbon number of not morethan 30 are more preferred. The “aliphatic alcohols” mentioned hereinclude alicyclic alcohols. Examples of these alcohols are octanol,decanol, dodecanol, stearyl alcohol, behenyl alcohol, ethylene glycol,diethylene glycol, glycerin, pentaerythritol,2,2-dihydroxyperfluoropropanol, neopentylene glycol,ditrimethylolpropane, and dipentaerythritol. These aliphatic carboxylicacid esters may contain aliphatic carboxylic acids and/or alcohols asimpurities. They may comprise a mixture of plural compounds. Examples ofthe aliphatic carboxylic acid esters are beeswax (a mixture mainlycomposed of myricyl palmitate), stearyl stearate, behenyl behenate,octyldodecyl behenate, glycerin monopalmitate, glycerin monostearate,glycerin distearate, glycerin tristearate, pentaerythritolmonopalmitate, pentaerythritol monostearate, pentaerythritol distearate,pentaerythritol tristearate, and pentaerythritol tetrastearate.

The release agent is contained in an amount of preferably not more than5 parts by weight, more preferably not more than 1 part by weight, basedon 100 parts by weight of the polycarbonate. If its content exceeds 5parts by weight, there may arise the problems such as decline ofhydrolytic resistance and contamination of the mold during injectionmolding. The said release agents may be used either singly or as acombination of two or more.

In the present invention, flame retardant may be added into thepolycarbonate resin composition, if required. It is known that apolycarbonate has relatively good flame retardancy as it is. Especially,a polycarbonate which can be obtained by a melting method and has aviscosity-average molecular weight of 16000 to 27000, and whose lossangle δ and complex viscosity η* (Pa·s) measured under the conditions of250° C. and an angular velocity of 10 rad/s satisfy the followingrelation (13): is excellent in flame retardancy and other properties asit is, and it may not be required to add a flame retardant.

4,700≦Tan δ/(η*)^(−0.87)≦6,000  (13)

In case of adding a flame retardant, as the flame retardant, metal saltof sulfonic acid compounds, halogen containing compounds, antimonycontaining compounds, phosphorus containing compounds, siliconecontaining compounds, or the like are exemplified. Of these, at leastone compound selected from the metal salt of sulfonic acid compounds is(are) preferred in view of preventing the reduction of mechanicalstrength.

As the metal salt of sulfonic acid compounds, metal salt of aliphaticsulfonic acid and metal salt of aromatic sulfonic acid are exemplified.As to the metal in the metal salt of sulfonic acid, alkaline metals suchas sodium, lithium, potassium, rubidium and cesium, and alkaline earthmetals such as beryllium, magnesium, calcium, strontium and barium, arepreferred. The said metal salt of sulfonic acid compound may be usedeither singly or as a combination of two or more.

Preferable examples of the metal salt of sulfonic acid compounds in viewof ability of flame retardancy and thermal stability, are metal salt ofaromatic sulfone sulfonic acid, perfluoroalkane-metal salt of sulfonicacid. Preferable examples of the metal salt of aromatic sulfone sulfonicacid are alkaline metal salt of aromatic sulfone sulfonic acid andalkaline earth metal salt of aromatic sulfone sulfonic acid, which maybe polymer compounds. Concrete examples of the metal salt of aromaticsulfone sulfonic acid are sodium salt of diphenylsulfone-3-sulfonicacid, potassium salt of diphenylsulfone-3-sulfonic acid, sodium salt of4,4′-dibromodiphenyl-sulfone-3-sulfonic acid, potassium salt of4,4′-dibromodiphenyl-sulfone-3-sulfonic acid, calcium salt of4-chloro-4′-nitrodiphenylsulfone-3-sulfonic acid, sodium salt ofdiphenylsulfone-3,3′-disulfonic acid and dipotassium salt ofdiphenylsulfone-3,3′-disulfonic acid.

Preferable examples of the perfluoroalkane-metal sulfonates areperfluoroalkane-alkaline metal sulfonates and perfluoroalkane-alkalineearth metal sulfonates, more preferably alkaline metal sulfonates havingC₄-C₈ perfluoroalkane group and alkaline earth metal sulfonates havingC₄-C₈ perfluoroalkane group. Concrete examples of theperfluoroalkane-metal sulfonates are perfluorobutane-sodium salt ofsulfonic acid, perfluorobutane- potassium salt of sulfonic acid,perfluoromethylbutane-sodium salt of sulfonic acid,perfluoromethylbutane-potassium salt of sulfonic acidperfluorooctane-sodium salt of sulfonic acid, perfluorooctane-potassiumsalt of sulfonic acid, perfluorobutane-tetraethyl ammonium salt ofsulfonic acid.

The flame retardant is contained in an amount of preferably not morethan 30 parts by weight based on 100 parts by weight of thepolycarbonate. If its content exceeds 30 parts by weight, the thermalstability thereof may be deteriorated.

As colorant, the compounds having an anthraquinone skeleton and thecompounds having a phthalocyanine skeleton can be used, the former beingpreferred in view of heat resistance.

Examples of the colorants usable in the present invention include thefollowing commercial products: MACROLEX Blue, MACROLEX Violet 3R andMACROLEX Violet B (Bayer AG), Sumiplast Violet RR, Sumiplast Violet Band Sumiplast Blue OR (Sumitomo Chemical Industries Co., Ltd.), DiaresinViolet D, Diaresin Blue G and Diaresin Blue N (Mitsubishi ChemicalCorporation).

Colorant is contained in an amount of preferably not more than 1 part byweight, more preferably not more than 0.5 part by weight based on 100parts by weight of the polycarbonate. It is possible to use either onecolorant or a mixture of two or more colorants.

The time and method of addition of the said additives such asstabilizer, ultraviolet absorber, release agent, flame retardant andcolorant are not specifically defined. Regarding the time of addition,the said additives may be added, for example (A) in the course ofpolymerization reaction, (B) on conclusion of the polymerizationreaction, or (C) after deactivation of the catalyst used for thepolymerization and before pelletization. They may be added when thepolycarbonate is in a molten state, such as in the course of kneading,but it is also possible to blend the additives with the polycarbonate ina solid state (such as in a state of pellet or powder) and then knead byan extruder. However, in view of inhibition of decomposition of theadditives and prevention of coloring, it is preferable to add theadditives either (a) in the course of polymerization reaction, (b) onconclusion of polymerization reaction, or (c) after deactivation of thecatalyst used for the polymerization.

As for the way of addition, the said additives may be directly mixed orkneaded with the polycarbonate or may be added after dissolving them ina suitable solvent or forming a high-concentration masterbatch with asmall quantity of polycarbonate or other resin. In case of using two ormore of these compounds, they may be added either separately or all atone time to the polycarbonate.

The present invention is also designed to provide a polycarbonate resincomposition having the desired properties, obtained by adding to thepolycarbonate various additives such as other type of thermoplasticresin, flame-retardant, impact resistance improver, antistatic agent,slip agent, anti-blocking agent, lubricant, defogging agent, naturaloil, synthetic oil, wax, organic filler, inorganic filler, etc., withinlimits not prejudicial to the object of the present invention.

EXAMPLES

The present invention is explained in more detail in the followingExamples, but it should be recognized that the scope of the presentinvention is not restricted to these Examples. The analyses and propertyevaluations of the obtained polycarbonates were made by the methodsdescribed below.

(1) Viscosity-average Molecular Weight (Mv)

Intrinsic viscosity [η] in methylene chloride at 20° C. was measured byan Ubbellohde viscometer, and viscosity-average molecular weight (Mv)was determined from the following equation.

[η]=1.23×10⁻⁴×(MV)^(0.83)

(2) Terminal Oh Group Content

Colorimetric determinations were made according to the titaniumtetrachloride/acetate method (Makromol. Chem. 88, 215 (1965)). Theweight of the terminal OH groups vis-á-vis the polycarbonate weight wasshown in ppm.

(3) Molecular Weight Distribution (Mw/Mn)

The molecular weight was determined by GPC with polystyrene calibrationusing a chromatograph HLC-8020 (Tosoh Corp.) with tetrahydrofuran aseluent, and Mw/Mn was calculated from the result of determinations.

(4) Dynamic Viscoelasticity

This was determined in the following way. The sample polycarbonate wasdried at 120° C. for 5 hours and press molded into a shape of 25 mm indiameter and 1.5 mm in thickness at 25° C. to obtain a sample formeasurement. The sample was dried in vacuo at 120° C. for 4 hours andthen subjected to measurement. A viscoelastometer RDA-700 (RheometricsScientific Co., Ltd.) equipped with a 25 mmφ parallel plate type fixturewas used, and the measuring atmosphere was set at 25° C. in a stream ofnitrogen which satisfies the adaptation conditions of theviscoelastometer. The measuring temperature was set by measuring thetemperature in the oven. Then the dried sample for measurement was setin position in the viscoelastomer and allowed to stand so that the wholesample would have the setting temperature, and measurement was made byrotating the sample with 10% strain at an angular velocity of 10 rad/s.From this measurement, loss tangent Tan δ and complex viscosity η*(Pa·s) were determined.

Further, the sample polycarbonate, dried at 120° C. for 5 hours, wasinjection molded by an injection molding machine M150AII-SJ (MeikiSeisakusho Ltd.) at a cylinder temperature of 280° C. to obtain the testpieces, and these test pieces were subjected to evaluation of flameretardancy and hydrolytic resistance.

(5) Impact Resistance

The polycarbonate was dried at 120° C. for 5 hours and then injectionmolded by an injection molding machine M150AII-SJ (mfd. by MeikiSeisakusho Co., Ltd.) at a cylinder temperature of 280° C. to make atest piece, and it was subjected to an ⅛ inch notched Izod impact testaccording to ASTM D-256 at room temperature (23° C.), 0° C. and −° C.The quotient of (frequency of ductile fracture)/(number of runs) wasshown as ductility.

(6) Transferability

The polycarbonate was dried at 120° C. for 5 hours and then injectionmolded by an injection molding machine SG75-Sicap MII (mfd. by SumitomoHeavy Industries Ltd.) under the conditions of 290° C. cylindertemperature, 90° C. mold temperature and one minute molding cycle byusing a mold for evaluation having a grained cavity surface. Theten-point average roughness (Rz) of the molded product was measuredaccording to JIS B 0601-1982, and the transfer rate for the nominalvalue of Rz (45.4 μm) of the mold for evaluation was determined.

Example 1

An example of the polycarbonate producing method according to thepresent invention is explained with reference to FIG. 1. FIG. 1 is aflow sheet of the production process in an embodiment of the presentinvention, in which reference numeral 1 indicates a diphenyl carbonate(DPC) tank, 2 agitators, 3 a bisphenol A (BPA) hopper, 4 a and 4 bmaterial mixing tanks, 5 a DPC flow rate control valve, 6 a BPA flowrate control valve, 7 a pump, 8 a catalyst flow rate control valve, 9 aprogram control unit, 10 a pump, 11 a catalyst tank, 12 by-productdischarge pipes, 13 a, 13 b and 13 c vertical polymerizers, 14 Max Blendagitator, 15 a horizontal polymerizer, and 16 gate paddle agitators.

A melt of diphenyl carbonate prepared at 120° C. in a nitrogen gasatmosphere and a bisphenol A powder weighed in a nitrogen gas atmospherewere metered by a micro-motion type flowmeter and a loss-in-weight typeweight feeder so that they would be fed at the rates of 205.0 mol/h fromthe DPC tank (1) and 197.1 mol/h (material molar ratio: 1.040) from theBPA hopper (3), respectively, and continuously supplied to the materialmixing tank (4 a) adjusted to 140° C. in a nitrogen atmosphere. Then themixed solution of materials was led into the material mixing tank (4 b)and then continuously supplied to the 100-liter first vertical stirringpolymerizer (13 a) by pump (7). Simultaneously with start of supply ofthe said mixture, there also was started continuous supply of an aqueoussolution of 2 wt % cesium carbonate to the polymerizer through its feedpipe at a flow rate of 1.1 mL/h (setting amount of catalyst: 0.35 μmolfor one mole of bisphenol A).

In this operation, the actual control of catalyst flow rate was made inthe program control unit (9) by calculating the setting flow rate ofcatalyst from the BPA flow rate detected by the BPA control valve (6)and the setting amount of catalyst, and controlling the opening of thecatalyst flow rate control valve (8) so that the calculated value wouldtally with the catalyst flow rate actually metered by a metering deviceattached to the said control valve (8).

The first vertical stirring polymerizer (13 a) provided with the MaxBlend agitator (14) was controlled at 220°C. in a nitrogen atmosphereunder normal pressure, and its liquid level was kept constant whilecontrolling the opening of the valve provided in the polymer dischargeline at the bottom of the polymerizer so that the average residence timewould become 60 min.

The polymerized solution discharged from the bottom of the polymerizerwas then successively supplied to the 100-liter vertical stirringpolymerizers (13 b, 13 c) provided with the second and third Max Blendagitator (14), respectively, and further to the 150-liter horizontalpolymerizer (15) provided with the fourth gate paddle agitator (16).

The reaction conditions in the second to fourth polymerizers were set sothat the temperature and the degree of vacuum would increase while thestirring rate would decrease with the progress of the reaction asspecified below.

Temperature Pressure Stirring rate 2nd polymerizer (13b) 220° C. 1.33 ×10⁴ Pa 110 rpm 3rd polymerizer (13c) 240° C.  2.0 × 10³ Pa  75 rpm 4thpolymerizer (15) 280° C. 2.66 × 10 Pa  10 rpm

During the reaction, the liquid level was controlled so that the averageresidence time in the second to fourth polymerizers would become 60minutes, and the phenol formed as a by-product in each polymerizer wasremoved through the by-product discharge pipe (12). The above operationwas run for 1,500 hours continuously under the said conditions. Thepolycarbonate drawn out from the polymer discharge port at the bottom ofthe fourth polymerizer was led in a molten state into a triple-ventedtwin-screw extruder where butyl p-toluenesulfonate was added in anamount of 2.8 ppm (4.5 times the neutralized amount of catalyst) basedon the weight of the polycarbonate, and the mixture was hydrogenated,evaporated and then pelletized.

The viscosity-average molecular weight (Mv) and the terminal OH groupcontent of the obtained polycarbonate were 21,800 and 500 ppm,respectively.

The time in which the actual amount of catalyst remained within therange of the setting amount of catalyst of ±0.06 μmol and ±0.1 μmolbased on mole of the aromatic dihydroxyl compound was calculated fromthe data of continuous metering of catalyst flow rate metered by themetering device attached to the catalyst flow rate control valve (8)(this data being hereinafter referred to as “continuous metering data ofcatalyst flow rate control valve”). The percentages of the timesatisfying the above specified ranges were 96.1% and 99.0%,respectively, of the whole production time. The molecular weightdistribution (Mw/Mn) and the value of Tan δ/(η*)^(−0.87) were 2.2 and5,980, respectively. The thus obtained polycarbonate is designated PC-1.

Example 2

The same procedure as defined in Example 1 was carried out except thatthe polycarbonate drawn out from the polymer discharge port at thebottom of the fourth polymerizer was led in a molten state into atriple-vented twin-screw extruder, and that after adding butylp-toluenesulfonate, hydrogenation and evaporation, there were furtheradded, based on 100 parts by weight of the polycarbonate, 0.05 part byweight of stabilizer 1, 0.05 part by weight of stabilizer 2, 0.3 part byweight of UV absorber 1, 0.02 part by weight of release agent 1, 0.0001part by weight of colorant 1 and 0.0001 part by weight of colorant 2,and the mixture was evaporated and pelletized. The polycarbonate used inthis Example is the same as that of Example 1 except that the aboveadditives were added, so that its viscosity-average molecular weight(Mv), terminal OH group content, molecular weight distribution (Mw/Mn)and Tan δ/(η*)^(−0.87) are the same as those of PC-1 of Example 1:21,800, 500 ppm, 2.2 and 5,980, respectively.

Example 3

The same procedure as defined in Example 1 was conducted except that thepolycarbonate discharged from the polymer discharge port at the bottomof the fourth polymerizer was led in a molten state into a triple-ventedtwin-screw extruder, and that after adding butyl p-toluenesulfonate,hydrogenation and evaporation, there were further added, based on 100parts by weight of the polycarbonate, 0.05 part by weight of stabilizer1 and 0.05 part by weight of flame retardant 1, and the mixture wasevaporated and then pelletized. The polycarbonate used in this Exampleis the same as that of Example 1 except that the above additives wereadded, so that its viscosity-average molecular weight (Mv), terminal OHgroup content, molecular weight distribution (Mw/Mn) and Tanδ/(η*)^(−0.87) are the same as those of PC-1 of Example 1: 21,800, 500ppm, 2.2 and 5,980, respectively.

Example 4

The same procedure as defined in Example 1 was conducted except that thecatalyst flow rate was changed to 1.60 mL/h (setting amount of catalyst:0.5 μmol for one mole of bisphenol A), that the pressure of the fourthpolymerizer was set at 6.67×10 Pa, and that butyl p-toluenesulfonate wasadded in an amount of 4.0 ppm (4.4 times the neutralized amount ofcatalyst) based on the weight of the polycarbonate. Theviscosity-average molecular weight (Mv) and the terminal OH groupcontent of the obtained polycarbonate were 21,500 and 500 ppm,respectively.

The time in which the actual amount of catalyst remained within therange of the setting amount of catalyst of ±0.06 μmol and ±0.1 μmol forone mole of the aromatic dihydroxyl compound was calculated from thecontinuous metering data of catalyst flow rate control valve. Thepercentages of the time satisfying the above specified ranges were 96.7%and 99.1%, respectively, of the whole production time. The molecularweight distribution (Mw/Mn) and the value of Tan δ/(η*)^(−0.87) were 2.3and 4,850, respectively. This polycarbonate is designated PC-2.

Example 5

The same procedure as defined in Example 1 was conducted except that thetemperature of the fourth polymerizer was set at 283°. Theviscosity-average molecular weight (Mv) and the terminal OH groupcontent of the obtained polycarbonate were 23,200 and 500 ppm,respectively.

The time in which the actual amount of catalyst remained within therange of the setting amount of catalyst of ±0.06 μmol and ±0.1 μmol forone mole of the aromatic dihydroxyl compound was calculated from thecontinuous metering data of catalyst flow rate control valve. Thepercentages of the time satisfying the above specified ranges were 96.5%and 99.3%, respectively, of the whole production time. The molecularweight distribution (Mw/Mn) and the value of Tan δ/(η*)⁻0.87 were 2.2and 5,720, respectively. This polycarbonate is designated PC-3.

Example 6

The same procedure as defined in Example 1 was conducted except that thesetting molar ratio of the starting materials was adjusted to be 1.035and the temperature of the fourth polymerizer was set at 285°. Theviscosity-average molecular weight (Mv) and the terminal OH groupcontent of the obtained polycarbonate were 25,300 and 530 ppm,respectively.

The time in which the actual amount of catalyst remained within therange of the setting amount of catalyst of ±0.06 μmol and ±0.1 μmol forone mole of the aromatic dihydroxyl compound was calculated from thecontinuous metering data of catalyst flow rate control valve. Thepercentages of the time satisfying the above specified ranges were 96.4%and 99.2%, respectively, of the whole production time. The molecularweight distribution (Mw/Mn) and the value of Tan δ/(η1*)^(−0.87) were2.3 and 5,550, respectively. This polycarbonate is designated PC-4.

Comparative Example 1

The same procedure as defined in Example 4 was conducted except that noprogram control unit was installed, and that the catalyst flow rate wasfixed at 1.6 mL/h (setting amount of catalyst: 0.5 μmol based on mole ofbisphenol A). The obtained polycarbonate had a viscosity-averagemolecular weight (Mv) of 22,400 and a terminal OH group content of 500ppm.

The time in which the actual amount of catalyst remained within therange of the setting amount of catalyst of ±0.06 μmol and ±0.1 μmol forone mole of the aromatic dihydroxyl compound was calculated from thecontinuous metering data of catalyst flow rate control valve. Thepercentages of the time satisfying the above specified ranges were 89.9%and 91.7%, respectively, of the whole production time. The molecularweight distribution (Mw/Mn) and Tan δ/(η*)^(−0.87) were 2.7 and 2,240,respectively. This polycarbonate is designated PC-5.

Comparative Example 2

Bisphenol A was dissolved in dichloromethane and polycondensed by theinterfacial method using triethylamine as polymerization catalyst, withthe terminal closed with a phenol. The obtained polycarbonate had aviscosity-average molecular weight (Mv) of 22,100 and a terminal OHgroup content of 30 ppm. The molecular weight distribution (Mw/Mn) andTan δ/(η*)^(−0.87) were 2.3 and 7,550, respectively. This polycarbonateis designated PC-6.

Comparative Example 3

The same procedure as defined in Example 4 was conducted except that thetemperature of the fourth polymerizer was set at 283° C. Theviscosity-average molecular weight (Mv) and the terminal OH groupcontent of the obtained polycarbonate were 23,500 and 520 ppm,respectively.

The time in which the actual amount of catalyst remained within therange of the setting amount of catalyst of ±0.06 μmol and ±0.1 μmol forone mole of the aromatic dihydroxyl compound was calculated from thecontinuous metering data of catalyst flow rate control valve. Thepercentages of the time satisfying the above specified ranges were 96.9%and 99.5%, respectively, of the whole production time. The molecularweight distribution (Mw/Mn) and the value of Tan δ/(η*)^(−0.87) were 2.3and 3,820, respectively. This polycarbonate is designated PC-7.

Comparative Example 4

The same procedure as defined in Example 4 was conducted except that thesetting molar ratio of the starting materials was adjusted to be 1.035and the temperature of the fourth polymerizer was set at 285° C. Theviscosity-average molecular weight (Mv) and the terminal OH groupcontent of the obtained polycarbonate were 25,400 and 590 ppm,respectively.

The time in which the actual amount of catalyst remained within therange of the setting amount of catalyst of ±0.06 μmol and ±0.1 μmol forone mole of the aromatic dihydroxyl compound was calculated from thecontinuous metering data of catalyst flow rate control valve. Thepercentages of the time satisfying the above specified ranges were 96.5%and 99.1%, respectively, of the whole production time. The molecularweight distribution (Mw/Mn) and the value of Tan δ/(η*)^(−0.87) were 2.3and 3,890, respectively. This polycarbonate is designated PC-8.

Comparative Example 5

The same procedure as defined in Comparative Example 4 was conductedexcept that no program control unit was installed, and that the catalystflow rate was fixed at 1.6 mL/h (setting amount of catalyst: 0.5 μmolbased on mole of bisphenol A). The obtained polycarbonate had aviscosity-average molecular weight (Mv) of 25,200 and a terminal OHgroup content of 530 ppm.

The time in which the actual amount of catalyst remained within therange of the setting amount of catalyst of ±0.06 μmol and ±0.1 μmol forone mole of the aromatic dihydroxyl compound was calculated from thecontinuous metering data of catalyst flow rate control valve. Thepercentages of the time satisfying the above specified ranges were 89.7%and 90.5%, respectively, of the whole production time. The molecularweight distribution (Mw/Mn) and the value of Tan δ/(η*)^(−0.87) were 2.9and 2,380, respectively. This polycarbonate is designated PC-9.

The materials used in the above Examples and Comparative Examples are asdescribed below. Stabilizer 1: tris(2,4-di-t-butylphenyl) phosphiteAdekastab 2112 produced by Asahi Denka Kogyo KK) Stabilizer 2:pentaerythrityl-tetrakis[3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate] (Irganox) 1010 produced by Ciba Specialty Chemicals Co.,Ltd.) UV absorber 1: 2-(2′-hydroxy-5′-t-octylphenyl)-benzotriazole(Seesorb 709 produced by Shipro Kasei K.K.) Release agent 1:pentaerythritol tetrastearate (Unistar H-476 produced by NOFCorporation) Flame retardant 1: potassium salt ofdiphenylsulfone-3-sulfonic acid (KSS produced by GE Ltd.) Colorant 1:MACROLEX Blue RR produced by Bayer AG Colorant 2: MACROLEX Violet 3Rproduced by Bayer AG

The evaluation results in Examples and Comparative Examples are shown inTable 1.

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Percentage of time satisfying settingamount of catalyst (%) ±0.06 μmol 96.1 — — 96.7 ±0.1 μmol 99.0 — — 99.1Viscosity-average molecular 21800 21800 21800 21500 weight (Mv) TerminalOH group content 500 500 500 500 (ppm) Molecular weight 2.2 2.2 2.2 2.3distribution (Mw/Mn) Complex viscosity η* (Pa · s) 1840 1840 1840 1720Loss tangent Tanδ 8.6 8.6 8.6 7.4 Tanδ/ (η*)^(−0.87) 5980 5980 5980 4850Formulation (Parts by weight) Polycarbonate Type PC-1 PC-1 PC-1 PC-2Amount 100 100 100 100 Stabilizer 1 — 0.05 0.05 — Stabilizer 2 — 0.05 —— UV absorber 1 — 0.3 — — Release agent 1 — 0.02 — — Flame retardant 1 —— 0.05 — Colorant 1 — 0.0001 — — Colorant 2 — 0.0001 — — Evaluationresults Impact resistance (J/m)/ Ductility At 23° C. 810 820 820 78010/10 10/10 10/10 10/10 At 0° C. 740 690 720 610 10/10 10/10 10/10 9/10At −30° C. 100 90 100 100 0/10 0/10 0/10 0/10 Transferability (%) 80 — —87 Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 5 Ex. 3 Percentage of timesatisfying setting amount of catalyst (%) ±0.06 μmol 89.9 — 96.5 96.9±0.1 μmol 91.7 — 99.3 99.5 Viscosity-average molecular 22400 22100 2320023500 weight (Mv) Terminal OH group content 500 30 500 520 (ppm)Molecular weight 2.7 2.3 2.2 2.3 distribution (Mw/Mn) Complex viscosityη* (Pa · s) 2040 1860 2860 2990 Loss tangent Tanδ 3.0 10.8 5.6 3.6Tanδ/(η*)^(−0.87) 2240 7550 5720 3820 Formulation (Parts by weight)Polycarbonate Type PC-5 PC-6 PC-3 PC-7 Amount 100 100 100 100 Stabilizer1 — — — — Stabilizer 2 — — — — UV absorber 1 — — — — Release agent 1 — —— — Flame retardant 1 — — — — Colorant 1 — — — — Colorant 2 — — — —Evaluation results — — — — Impact resistance (J/m)/ Ductility At 23° C.760 820 820 810 10/10 10/10 10/10 10/10 At 0° C. 350 780 800 750 4/1010/10 10/10 10/10 At −30° C. 90 130 390 130 0/10 0/10 5/10 0/10Transferability (%) 90 68 — — Comp. Comp. Ex. 6 Ex. 4 Ex. 5 Percentageof time satisfying setting amount of catalyst (%) ±0.06 μmol 96.4 96.589.7 ±0.1 μmol 99.2 99.1 90.5 Viscosity-average molecular 25300 2540025200 weight (Mv) Terminal OH group content 530 590 530 (ppm) Molecularweight 2.3 2.3 2.9 distribution (Mw/Mn) Complex viscosity η* (Pa · s)4010 4180 4450 Loss tangent Tanδ 4.1 2.7 1.6 Tanδ/(η*)^(−0.87) 5550 38902380 Formulation (Parts by weight) Polycarbonate Type PC-4 PC-8 PC-9Amount 100 100 100 Stabilizer 1 — — — Stabilizer 2 — — — UV absorber 1 —— — Release agent 1 — — — Flame retardant 1 — — — Colorant 1 — — —Colorant 2 — — — Evaluation results Impact resistance (J/m)/ DuctilityAt 23° C. 820 820 800 10/10 10/10 10/10 At 0° C. 820 810 720 10/10 10/1010/10 At −30° C. 730 300 110 10/10 2/10 0/10 Transferability (%) — — —

What is claimed is:
 1. A polycarbonate which can be obtained by amelting method using an aromatic dihydroxyl compound and a carbonic aciddiester as starting materials and has a viscosity-average molecularweight of 16000 to 27000, and whose loss angle δ and complex viscosityη* (Pa·s) measured under the conditions of 250° C. and an angularvelocity of 10 rad/s satisfy the following relation (1): 4,700≦Tanδ/(η*)^(−0.87)  (1).
 2. A polycarbonate according to claim 1 having aterminal OH group content in the range of 50 to 1,000 ppm.
 3. Apolycarbonate resin composition comprising a polycarbonate which can beobtained by a melting method using an aromatic dihydroxyl compound and acarbonic acid diester as starting material and has a viscosity-averagemolecular weight of 16000 to 27000, and whose loss angle δ and complexviscosity η* (Pa·s) measured under the conditions of 250° C. and anangular velocity of 10 rad/s satisfy the following relation (1):4,700≦Tan δ/(η*)^(−0.87)  (1).
 4. A polycarbonate composition accordingto claim 3, wherein a terminal OH group content of the polycarbonate is50 to 1,000 ppm.
 5. A polycarbonate resin composition according to claim3 containing at least one additive selected from stabilizer, ultravioletabsorber, release agent, flame retardant and colorant.
 6. Apolycarbonate resin composition according to claim 5 wherein thestabilizer is at least one antioxidant selected from the hindered phenolcompounds and phosphorus compounds.
 7. A polycarbonate resin compositionaccording to claim 5, wherein the ultraviolet absorber is at least onecompound selected from benzotriazole compounds,2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]-phenol,2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl]-5-(octyloxy)phenol,2,2′-(1,4-phenylene)bis[4H-3,1-benzoxadine-4-one], and[(4-methoxyphenyl)-methylene]-propanedioic acid-dimethyl ester.
 8. Apolycarbonate resin composition according to claim 5, wherein therelease agent is at least one compound selected from the aliphaticcarboxylic acids and aliphatic carboxylic acid esters.
 9. Apolycarbonate resin composition according to claim 5, wherein the flameretardant is at least one compound selected from the metal salt ofsulfonic acid compounds.
 10. A polycarbonate resin composition accordingto claim 5, wherein the colorant is a compound having an anthraquinoneskeleton.
 11. A polycarbonate resin composition according to claim 5,wherein the additives are added (a) in the course of the polymerizationreaction for producing the polycarbonate as defined in claim 1, (b) atthe end of said polymerization reaction, or (c) after deactivation ofthe catalyst used for the polymerization by a catalyst deactivator andbefore pelletization.